The nervous system must receive and process information about the world outside in order to react, communicate, and keep the body healthy and safe. Much of this information comes through the sensory organs: the eyes, ears, nose, tongue, and skin. Specialized cells and tissues within these organs receive raw stimuli and translate them into signals the nervous system can use. Nerves relay the signals to the brain, which interprets them as sight (vision), sound (hearing), smell (olfaction), taste (gustation), and touch (tactile perception).

1. The Eyes Translate Light into Image Signals for the Brain to Process

The eyes sit in the orbits of the skull, protected by bone and fat. The white part of the eye is the sclera. It protects interior structures and surrounds a circular portal formed by the cornea, iris, and pupil. The cornea is transparent to allow light to enter the eye, and curved to direct it through the pupil behind it. The pupil is actually an opening in the colored disk of the iris. The iris dilates or constricts, adjusting how much light passes through the pupil and onto the lens. The curved lens then focuses the image onto the retina, the eye’s interior layer. The retina is a delicate membrane of nervous tissue containing photoreceptor cells. These cells, the rods and cones, translate light into nervous signals. The optic nerve carries the signals from the eye to the brain, which interprets them to form visual images.

2. The Ear Uses Bones and Fluid to Transform Sound Waves into Sound Signals

Music, laughter, car honks — all reach the ears as sound waves in the air. The outer ear funnels the waves down the ear canal (the external acoustic meatus) to the tympanic membrane (the “ear drum”). The sound waves beat against the tympanic membrane, creating mechanical vibrations in the membrane. The tympanic membrane transfers these vibrations to three small bones, known as auditory ossicles, found in the air-filled cavity of the middle ear. These bones – the malleus, incus, and stapes – carry the vibrations and knock against the opening to the inner ear. The inner ear consists of fluid-filled canals, including the spiral-shaped cochlea. As the ossicles pound away, specialized hair cells in the cochlea detect pressure waves in the fluid. They activate nervous receptors, sending signals through the cochlear nerve toward the brain, which interprets the signals as sounds.

3. Specialized Receptors in the Skin Send Touch Signals to the Brain

Skin consists of three major tissue layers: the outer epidermis, middle dermis, and inner hypodermis. Specialized receptor cells within these layers detect tactile sensations and relay signals through peripheral nerves toward the brain. The presence and location of the different types of receptors make certain body parts more sensitive. Merkel cells, for example, are found in the lower epidermis of lips, hands, and external genitalia. Meissner corpuscles are found in the upper dermis of hairless skin — fingertips, nipples, the soles of the feet. Both of these receptors detect touch, pressure, and vibration. Other touch receptors include Pacinian corpuscles, which also register pressure and vibration, and the free endings of specialized nerves that feel pain, itch, and tickle.

4. Olfaction: Chemicals in the Air Stimulate Signals the Brain Interprets as Smells

The sense of smell is called olfaction. It starts with specialized nerve receptors located on hairlike cilia in the epithelium at the top of the nasal cavity. When we sniff or inhale through the nose, some chemicals in the air bind to these receptors. That triggers a signal that travels up a nerve fiber, through the epithelium and the skull bone above, to the olfactory bulbs. The olfactory bulbs contain neuron cell bodies that transmit information along the cranial nerves, which are extensions of the olfactory bulbs. They send the signal down the olfactory nerves, toward the olfactory area of the cerebral cortex.

5. Home of the Taste Buds: The Tongue Is the Principal Organ of Gustation

What are all those small bumps on the top of the tongue? They’re called papillae. Many of them, including circumvallate papillae and fungiform papillae, contain taste buds. When we eat, chemicals from food enter the papillae and reach the taste buds. These chemicals (or tastants) stimulate specialized gustatory cells inside the taste buds, activating nervous receptors. The receptors send signals to fibers of the facial, glossopharyngeal, and vagus nerves. Those nerves carry the signals to the medulla oblongata, which relays them to the thalamus and cerebral cortex of the brain.

Credit : Visible body 

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'Forever chemicals' or PFAS are widely present in non-stick kitchenware, plastics, water-resistant materials, paints, carpets and clothes. On entering the body they accumulate in the bloodstream, and impact gut flora or lungs, causing asthma and other diseases.

As PFAS bind to serum proteins in the blood, regular blood or plasma donations result in a significant reduction in blood PFAS levels; plasma donations were more effective, corresponding to a 30 per cent decrease.

Although results suggest that this is a viable tool for removing PFAS from the bloodstream, what does it mean for recipients of the blood? Potential recipients are very likely to already have PFAS in their bloodstream, and there is no data to suggest that receiving blood contaminated with the compounds exposes them to additional risks.

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In 1954, the kidney was the first human organ to be transplanted successfully. Until the early 1980s, the potential of organ rejection limited the number of transplants performed.

 The first ever successful transplant of any organ was done at the Brigham & Women's Hospital in Boston, Ma. The surgery was done by Dr. Joseph Murray, who received the Nobel Prize in Medicine for his work. The reason for his success was due to Richard and Ronald Herrick of Maine. Richard Herrick was a in the Navy and became severely ill with acute renal failure. His brother Ronald donated his kidney to Richard, and Richard lived another 8 years before his death. Before this, transplant recipients didn't survive more than 30 days. The key to the successful transplant was the fact that Richard and Ronald were identical twin brothers and there was no need for anti-rejection medications, which was not known about at this point. This was the most pivotal moment in transplant surgery because now transplant teams knew that it could be successful and the role of rejection/anti-rejection medicine.

Credit : Wikipedia 

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Organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organs may be transported from a donor site to another location. Organs and/or tissues that are transplanted within the same person's body are called autografts. Transplants that are recently performed between two subjects of the same species are called allografts. Allografts can either be from a living or cadaveric source.

Organs that have been successfully transplanted include the heart, kidneys, liver, lungs, pancreas, intestine, thymus and uterus. Tissues include bones, tendons (both referred to as musculoskeletal grafts), corneae, skin, heart valves, nerves and veins. Worldwide, the kidneys are the most commonly transplanted organs, followed by the liver and then the heart. Corneae and musculoskeletal grafts are the most commonly transplanted tissues; these outnumber organ transplants by more than tenfold.

Organ donors may be living, brain dead, or dead via circulatory death. Tissue may be recovered from donors who die of circulatory death, as well as of brain death – up to 24 hours past the cessation of heartbeat. Unlike organs, most tissues (with the exception of corneas) can be preserved and stored for up to five years, meaning they can be "banked". Transplantation raises a number of bioethical issues, including the definition of death, when and how consent should be given for an organ to be transplanted, and payment for organs for transplantation. Other ethical issues include transplantation tourism (medical tourism) and more broadly the socio-economic context in which organ procurement or transplantation may occur. A particular problem is organ trafficking.[5] There is also the ethical issue of not holding out false hope to patients.

Transplantation medicine is one of the most challenging and complex areas of modern medicine. Some of the key areas for medical management are the problems of transplant rejection, during which the body has an immune response to the transplanted organ, possibly leading to transplant failure and the need to immediately remove the organ from the recipient. When possible, transplant rejection can be reduced through serotyping to determine the most appropriate donor-recipient match and through the use of immunosuppressant drugs.

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Human blood is red because of the protein hemoglobin, which contains a red-colored compound called heme that’s crucial for carrying oxygen through your bloodstream. Heme contains an iron atom which binds to oxygen; it’s this molecule that transports oxygen from your lungs to other parts of the body.

Chemicals appear particular colors to our eyes based on the wavelengths of light they reflect. Hemoglobin bound to oxygen absorbs blue-green light, which means that it reflects red-orange light into our eyes, appearing red. That’s why blood turns bright cherry red when oxygen binds to its iron. Without oxygen connected, blood is a darker red color.

Carbon monoxide, a potentially deadly gas, can also bind to heme, with a bond around 200 times stronger than that of oxygen. With carbon monoxide in place, oxygen can’t bind to hemoglobin, which can lead to death. Because the carbon monoxide doesn’t let go of the heme, your blood stays cherry red, sometimes making a victim of carbon monoxide poisoning appear rosy-cheeked even in death.

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